1. Field of the Invention
This invention pertains to the use of electromagnetic force/torque for control of motion in unpowered apparatus and apparatus driven by electric motors and/or other prime movers.
2. Description of the Related Art
Power control (PC) refers to control over the power generated at one or more input to an electromechanical apparatus. Prior-art power control mainly deals with relatively large apparatus. U.S. Pat. No. 6,380,709 (Nishimura et al.) teaches an improved means of driving a motor, using controlled switching of power transistors, to obtain better rotation characteristics. U.S. Pat. No. 6,359,410 (Randolph et al.) teaches the use of resistive sensing to better control the maximum current applied to the motor. U.S. Pat. No. 5,349,276 (Mezzatesta et al.) utilizes an electronic tachometer to monitor motor speed accurately, and feed this information to a control system for controlling speed reliably, in a safe-operating regime. U.S. Pat. No. 6,344,721 (Seki et al.) and U.S. Pat. No. 6,340,873 (Seki et al.) describe a semiconductor integrated circuit for brushless motor drive control.
Power transmission control (PTC) refers to control over the power transmitted to an electro-mechanical apparatus. Prior-art power transmission control is also primarily targeted at relatively large industrial applications. U.S. Pat. No. 6,157,147 (Lin et al.) and U.S. Pat. No. 6,346,784 Lin et al.) teach the use of an eddy-current clutch to transmit power, after suitable speed translation. U.S. Pat. No. 5,586,636 (Linnig et al.) teaches the use of an eddy-current clutch in conjunction with a friction clutch, to transmit power for the fan wheel of an internal/external combustion (IC/EC) engine.
Load control (LC) refers to control over the total resistive force presented by an electro-mechanical apparatus. Prior-art load control includes eddy-current and hysteresis brakes. U.S. Pat. No. 6,460,828 (Gersemsky et al.) describes an eddy-current brake for a hoist, where a set of permanent magnets is selectively positioned to generate variable eddy-current force in an induction member, thus braking the hoist. The magnets move radially outwards to increase the braking force and reduce the speed. The use of controllable braking torque by moving an induction disk has been used in Ferraris meters to measure power. U.S. Pat. No. 6,062,350 mentions the use of conductors of varying thickness, conductivity, etc. for braking an amusement car on a track. U.S. Pat. No. 6,185,373 describes a camera with an induction brake. Here, the device is used to apply braking force, to stop the motion of the camera shutter, under control of the control circuitry.
Apparatus having rest states have been described in U.S. Pat. No. 6,538,541 (Kralik), where a two-position switch is described, using a coil to move an armature between the two positions. U.S. Pat. No. 6,532,136 (Bae et al.) describes a hard-disk drive magnetic latch, with a coil that is energized for normal operation and de-energized for parking. U.S. Pat. No. 4,706,055 (Uetsuhara) describes an electromagnetic actuator having a member with a multiplicity of poles, in proximity with a magnet whose flux is modulated by a coil.
In various scientific demonstrations in which inductive force is used, the single mention of timing control is dropping a neodymium magnet down an inclined plane with a conductive member embedded in the plane, and slowing down of the magnet when it goes over the conductive member. Other prior art involves a pendulum consisting of a solid or slotted conducting member oscillating near a magnet, where slotting the conducting member greatly increases the stopping time.